An ergometer is commercially available which comprises a flywheel which is driven by the legs of the operator, and a belt for applying load to the flywheel by friction. The amount of the applied load is controlled by adjusting a weight which is provided at the end of the belt. The ergometer is advantageous in that, in the case when the flywheel is turned at a constant speed, the amount of load can be obtained directly from the value of the weight. It is disadvantageous, however, in that the measurement of the load takes a relatively long time, the size of the load is large, and adjustment of the load is intricate.
Recently, an ergometer with electrical loading means also became available in the market. One such ergometer comprises a flywheel made of gray cast iron, a rotation sensor for detecting the speed of rotation of the flywheel, and a torque detecting strain gauge. To obtain predetermined torque in the ergometer, the current supplied to the electromagnetic brake is controlled according to a relation between the output of the strain gauge and the speed of rotation of the flywheel.
In another example, the relation between the flywheel's speed and torque and the control current value are calculated by a computer or the like in advance and stored in a memory unit. According to the instruction code of a program, current to be applied to the braking coil is determined from the speed of rotation of the flywheel and a desired braking force to obtain a predetermined torque.
The torque detecting means of the former ergometer is mechanical, and an intricate adjustment must be carried out before the ergometer is operated or after it has been used for a long time. In the latter ergometer, complicated calculations must be performed, and it is necessary to provide another memory unit for storing the results of calculations as data. In these ergometers, the loading means is electrically controlled to obtain the predetermined torque.
Each of the electric ergometers has the further disadvantage in that, because the flywheel is made up of a stator and a rotor provided inside the stator, the stator must have exciting coils that are large in size. Accordingly, the loading device is also large in size, and the rotor inside the stator is maintained at a high temperature.
A variety of bicycle ergometers have been proposed as training units in which, according to an instruction from a microcomputer incorporated therein, physical attributes (age, weight, sex and the number of pulses per minute) of a person are inputted and processed to calculate an optimum load value and the number of pulses for control under the optimum load. The object is to control the exercise of the user continuously according to the data thus calculated.
In the above-described method for use of the ergometers, the optimum load value is calculated with the static elements (age, sex, weight, and rest number of pulses) of the physical conditions as data, and can be used as a reference when the user exercises continuously. However, in the determination of the optimum load value, no variation of the physical characteristics of the user which occur during continuous exercise are taken into consideration. Therefore, the optimum load value that is calculated cannot be used for all the users. That is, depending on the user, the number of pulses per minute reaches the athletic maximum number of pulses per minute before it reaches the steady number of pulses per minute which is provided under the optimum load.
In order to obtain the steady number of pulses per minute of a person under accurate optimum load, the following method should be employed. First, the load of a rotary exercising device driven by a user is increased stepwise, so that the steady number of pulses per minute is measured under an increasing load until the user indicates that the exercise cannot be continued any longer. Next, a load value corresponding to about 70% of the number of pulses per minute of the athletic maximum, which is generally called the "athletic optimum number of pulses per minute", is calculated.
The above-described method is accurate; however, it suffers from the drawbacks in that the user must continue exercising until the athletic optimum number of pulses per minute is reached. Practicing this method may, therefore, be hazardous to the user. Also, the measurement takes a relatively long time to complete.